Disazo compound, method for preparing the same, and electrophotographic element containing the same for use in electrophotography

ABSTRACT

This invention relates to a disazo compound, a method for producing said disazo compound and an electrophotographic element containing said disazo compound, said disazo compound has the general formula (I), ##STR1## wherein Y represents a substituted or non-substituted cyclic hydrocarbon or substituted or non-substituted heterocycle; R represents hydrogen, substituted or non-substituted alkyl group, or substituted or non-substituted phenyl group; and Z represents a substituted or non-substituted cyclic hydrocarbon or heterocycle fused with phenyl nucleus.

BACKGROUND OF THE INVENTION

This invention relates to a diazo compound, method for preparing thesame, and electrophotographic element containing the same for use inelectrophotography. More particularly, this invention relates to anelectrophotographic element having a photosensitive layer containing adisazo compound as a charge generating substance which generates acharge carrier by light irradiation.

Heretofore, there were used inorganic photosensitive materials such asselenium, selenium alloy, cadmium sulfide, zinc oxide and the like.Among them, selenium type photosensitive material was widely usedbecause it has generally superior properties in respect of receivingpotential, dark decay, sensitivity and the like. However, the seleniumtype electrophotographic element has such disadvantages as that thecontrol of properties is difficult since it is prepared by vapordeposition; that the manufacturing cost is high; that it is difficult towork the element into a belt-like product due to lack of flexibility;and that the handling of the element is not easy because it is toosensitive to mechanical impact and heat.

There was also used an element having a photosensitive layer containingan organic photosensitive material superior in flexibility and easy inproduction, for example, a charge transfer complex of2,4,7-trinitro-9-fluorenone and poly-N-vinylcarbazole. However, thesensitivity of this element was too low and therefore unsuitable as anelectrophotographic element for a high speed copying machine.

Recently, various studies have been carried out to remove disadvantagesfor these electrophotographic elements. Among them, there is noted aseparate function type electrophotographic element wherein thegeneration of a charge carrier and the transfer of the generated chargecarrier are respectively conducted by separate substances. As theseparate function type electrophotographic element, there can enumerateda laminated type electrophotographic element having a photosensitivelayer prepared by laminating a charge generating layer containing acharge generating substance to generate a charge carrier by lightirradiation and a charge transfer layer containing a charge transfersubstance to transfer the generated charge, a dispersed typeelectrophotographic element prepared by dispersing a charge generatingsubstance in a charge transfer medium containing a charge transfersubstance, and the like. Since these photosensitive materials are widelyselected and it is possible to enhance the sensitivity, they are notedas an electrophotographic element for a plain paper copier.

Examples of these electrophotographic elements include:

(1) a laminated type electrophotographic element using a thin layerformed by vapor depositing perillene derivatives as a charge generatinglayer and oxadiazole derivatives as a charge transfer layer (U.S. Pat.No. 3,871,882);

(2) a laminated type electrophotographic element using a thin layerformed by coating an organic amine solution of Chloro Dian Blue as acharge generating layer and hydrazone compound as a charge transferlayer (Japanese Patent Publication No. 55-42380); and the like.

However, these conventional laminated type electrographic elements havenot only advantages but also various disadvantages. For example, theabove electrophotographic element (1) using perillene derivatives andoxadiazole derivatives has a disadvantage that the manufacturing cost isvery high because of forming a charge generating layer by vapordeposition. The above electrophotographic element (2) using Chloro DianBlue and hydrazone compound must use an organic amine (for example,ethylene diamine) as a coating solvent for forming a charge generatinglayer, which is difficult in handling.

As a photosensitive material having a good sensitivity which can beeasily manufactured, there are enumerated a photosensitive materialusing a disazo pigment having styrylstilbene structure as a chargegenerating substance (Japanese Laid Open No. 53-133445); aphotosensitive material using a diazo pigment having dibenzothiophenestructure as a charge generating substance (Japanese Laid Open No.54-21728); a photosensitive material using a disazo pigment havingcarbazole structure (Japanese Laid Open Nos. 53-95033 and 53-95966); aphotosensitive material using a trisazo pigment having triphenyl aminestructure (Japanese Laid Open No. 53-132347); a photosensitive materialusing a disazo pigment having oxazole structure (Japnese Laid Open No.54-12742); a photosensitive material using a disazo pigment havingdisstyrylcarbazole structure (Japanese Laid Open No. 54-14967); aphotosensitve material using a disazo pigment having bisstilbenestructure (Japanese Laid Open No. 54-17733); a photosensitive materialusing a disazo pigment having fluorenone structure (Japanese Laid OpenNo. 54-22834); and the like. However, these conventionalphotosensitizers also have merits and demerits, and a development of newphotosensitive materials having better properties is desired.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a disazo compoundexpressed by the general formula (I), ##STR2## wherein Y represents asubstituted or non-substituted cyclic hydrocarbon or substituted ornon-substituted heterocycle; R represents hydrogen, substituted ornon-substituted alkyl group, or substituted or non-substituted phenylgroup; and Z represents a substituted or non-substituted cyclichydrocarbon or substituted or non-substituted heterocycle fused withphenyl nucleus.

Another object of the present invention is to provide a method forpreparing a disazo compound expressed by the neneral formula (I),##STR3## wherein Y, R and Z are the same as mentioned above,characterized by diazotizing 4,4'-diaminotriphenyl amine expressed bythe general formula (II), ##STR4## to produce a tetrazonium saltexpressed by the general formula (III), wherein X represents an anionfunctional group, and reacting the thus produced tetrazonium salt with acoupler expressed by the general formula (IV), ##STR5## wherein Y, R andZ are the same as mentioned above.

The other object of the present invention is to provide a photosensitivematerial for use in electrophotography, characterized by that saidphotosensitive material has on an electroconductive substrate aphotosensitive layer containing a disazocompound expressed by thegeneral formula (V), ##STR6## wherein A represents a residue of acoupler.

DETAILED DESCRIPTION OF THE INVENTION

Examples of the cyclic hydrocarbon of Y in the general formula (I) ofthe disazocompound of the present invention include benzene ring,naphthalene ring or the like, and examples of the heterocycle of Yinclude dibenzofuran ring, carbazole ring or the like. Examples of asubstituent of the cyclic hydrocarbon or heterocycle of Y include alower alkyl group such as methyl, ethyl, propyl, butyl and the like; alower alkoxy group such as methoxy, ethoxy, butoxy and the like; a lowerdialkyl amino group such as N,N-dimethylamino, N,N-diethylamino,N,N-dibutylamino groups and the like; a halogen atom such as fluorine,chlorine, bromine and the like; a halomethyl group such astrifluoromethyl and the like; a lower alkylcarboxyl group such asethylcarboxyl group; carboxyl group; cyano group; nitro group; --SO₃ Naand the like.

Examples of the alkyl group of R include a lower alkyl group such asmethyl, ethyl, and the like. Examples of the substituent of the alkylgroup or phenyl group of R include a halogen atom such as chlorine.

Examples of the cyclic hydrocarbon of Z include benzene ring,naphthalene ring, and the like, and examples of the heterocycle includeindole ring, benzofuran ring, carbazole ring and the like. Examples ofthe substituent of the cyclic hydrocarbon or the heterocycle include ahalogen atom such as chlorine.

Examples of the coupler of the disazocompounds expressed by the generalformula (V) include a compound having a phenolic hydroxyl group such asphenol type, naphthol type compounds and the like; an aromatic aminocompound having an anino group; an aminonaphthol type compound having anamino group and a phenolic hydroxyl group; a compound having analiphatic or aromatic enol type ketone group (active methylene group);and the like. Preferably, the residue A of the coupler is expressed bythe following general formula (VI), (VII), (VIII), (IX), (X), (XI),(XII), (XIII), (XIV), (XV), (XVI), (XVII) and (XVIII). ##STR7## whereinX₁, Y₁, Z, m and n in the above formula (VI), (VII), (VIII) and (IX)represent the following groups: ##STR8## (wherein R₁ and R₂ representhydrogen or a substituted or non-substituted alkyl group, and R₃represents a substituted or non-substituted alkyl or a substituted ornon-substituted aryl group);

Y₁ : hydrogen, halogen, substituted or non-substituted alkyl group,substituted or non-substituted alkoxy group, carboxyl group, sulfogroup, substituted or non-substituted sulfamoyl group or ##STR9##(wherein R₄ represents hydrogen, alkyl group or its substitutedcompound, phenyl group or its substituted compound, and Y₂ representscyclic hydrocarbon or its substituted compound, heterocycle or itssubstituted compound, ##STR10## wherein R₅ represents a cyclichydrocarbon or its substituted compound, heterocycle or its substitutedcompound, or styryl group or its substituted compound, and R₆ representshydrogen, alkyl group, phenyl group or their substituted compound, or R₅and R₆ may form a ring with carbons bonded thereto);

Z: cyclic hydrocarbon or its substituted compound, or heterocycle or itssubstituted compound;

n: an integer of 1 or 2;

m: an integer of 1 or 2. ##STR11## wherein R₇ in the above formula (X)and (XI) represents a substituted or non-substituted hydrocarbonylgroup, and X₁ is the same as mentioned above. ##STR12## wherein R₈represents an alkyl group, carbamoyl group, carboxyl group or its ester,and Ar₁ represents a cyclic hydrocabon or its substituted compound, andX₁ is the same as mentioned above. ##STR13## wherein R₉ in the aboveformula (XIII) and (XIV) represents hydrogen or substituted ornon-substituted hydrocarbonyl group, and Ar₂ represents cyclichydrocarbon or its substituted compound.

Examples of the cyclic hydrocarbon expressed by Z in the above generalformula (VI), (VII), (VIII) or (IX) include benzene ring, naphthalenering and the like, and examples of the heterocycle expressed by the sameinclude indole ring, carbazole ring, benzofuran ring, dibenzofuran ringand the like. Examples of the substituent of the ring expressed by Zinclude a halogen atom such as chlorine, bromine, and the like.

Examples of the cyclic hydrocarbon expressed by Y₂ or R₅ include phenyl,naphthyl, anthryl, pyrenyl and the like, and examples of theheterocyclic group expressed by the same include pyridyl, thienyl,furyl, indolyl, benzofuranyl, carbazolyl, dibenzofuranyl and the like.Examples of the ring formed by bonding R₅ and R₆ include fluorene ring.

Examples of the substituents for the cyclic hydrocarbon or heterocycleexpressed by Y₂ or R₅ or for the ring formed by bonding R₅ and R₆include an alkyl group such as methyl, ethyl, propyl, butyl or the like;an alkoxy group such as methoxy, ethoxy, propoxy, butoxy or the like; ahalogen atom such as chlorine, bromine or the like; a dialkyl aminogroup such as dimethyl amino, diethyl amino or the like; a diaralkylamino group such as dibenzyl amino or the like; a halomethyl group suchas trifluoromethyl or the like; nitro group; cyano group; carboxyl groupor its ester; hydroxyl group; sulphonate group such as --SO₃ Na; and thelike.

Examples of the substituent for the phenyl group expressed by R₄ includea halogen atom such as chlorine or bromine.

Examples of the hydrocarbonyl group expressed by R₇ and R₉ include analkyl group such as methyl, ethyl, propyl, butyl and the like; anaralkyl group such as benzyl and the like; an aryl group such as phenyl;or their substituted compounds.

Examples of the substituent for the hydrocarbonyl group expressed by R₇or R₉ include an alkyl group such as methyl, ethyl, propyl, butyl andthe like; an alkoxy group such as methoxy, ethoxy, propoxy, butoxy andthe like; a halogen atom such as chlorine, bromine and the like;hydroxyl group; nitro group; and the like.

Examples of the cyclic hydrocarbon expressed by Ar₁ or Ar₂ includephenyl, naphthyl and the like, and examples of the substituents forthese groups include an alkyl group such as methyl, ethyl, propyl, butylor the like; an alkoxy group such as methoxy, ethoxy, propoxy, butoxy orthe like; nitro group; a halogen group such as chlorine, bromine or thelike; cyano group; and a dialkyl amino group such as dimethyl amino,diethyl amino or the like.

Among the groups expressed by X₁, hydroxyl group is particularlysuitable.

Among the above coupler residues, preferable ones are expressed by thegeneral formula (VII), (X), (XI), (XII), (XIII) and (XIV), and X₁ in thegeneral formula is preferably hydroxyl group. Among them, the couplerresidue expressed by the general formula (XV) ##STR14## (wherein Y₁ andZ are the same as mentioned above) is preferable, and the couplerresidue expressed by the general formula (XVI) ##STR15## (wherein Z, Y₂and R₂ are the same as mentioned above) is more preferable.

Still more preferable coupler residue among the above mentioned groupsis expressed by the general formula (XVII) or (XVIII) ##STR16## (whereinZ, R₂, R₅ and R₆ are the same as mentioned above, and R₁₀ is the same asthose illustrated with regard to the substituents for Y₂).

Examples of the disazo compound of the present invention are illustratedby the folowing structural formula showing the coupler residue A.

    __________________________________________________________________________     ##STR17##                                                                    Disazo                        Disazo                                          Pigment                       Pigment                                         No.  A                        No.  A                                          __________________________________________________________________________       ##STR18##                  2                                                                                ##STR19##                                    3                                                                                ##STR20##                  4                                                                                ##STR21##                                    5                                                                                ##STR22##                  6                                                                                ##STR23##                                    7                                                                                ##STR24##                  8                                                                                ##STR25##                                    9                                                                                ##STR26##                  10                                                                               ##STR27##                                    11                                                                               ##STR28##                  12                                                                               ##STR29##                                    13                                                                               ##STR30##                  14                                                                               ##STR31##                                    15                                                                               ##STR32##                  16                                                                               ##STR33##                                    17                                                                               ##STR34##                  18                                                                               ##STR35##                                    19                                                                               ##STR36##                  20                                                                               ##STR37##                                    21                                                                               ##STR38##                  22                                                                               ##STR39##                                    23                                                                               ##STR40##                  24                                                                               ##STR41##                                    25                                                                               ##STR42##                  26                                                                               ##STR43##                                    27                                                                               ##STR44##                  28                                                                               ##STR45##                                    29                                                                               ##STR46##                  30                                                                               ##STR47##                                    31                                                                               ##STR48##                  32                                                                               ##STR49##                                    33                                                                               ##STR50##                  34                                                                               ##STR51##                                    35                                                                               ##STR52##                  36                                                                               ##STR53##                                    37                                                                               ##STR54##                  38                                                                               ##STR55##                                    39                                                                               ##STR56##                  40                                                                               ##STR57##                                    41                                                                               ##STR58##                  42                                                                               ##STR59##                                    43                                                                               ##STR60##                  44                                                                               ##STR61##                                    45                                                                               ##STR62##                  46                                                                               ##STR63##                                    47                                                                               ##STR64##                  48                                                                               ##STR65##                                    49                                                                               ##STR66##                  50                                                                               ##STR67##                                    51                                                                               ##STR68##                  52                                                                               ##STR69##                                    53                                                                               ##STR70##                  54                                                                               ##STR71##                                    55                                                                               ##STR72##                  56                                                                               ##STR73##                                    57                                                                               ##STR74##                  58                                                                               ##STR75##                                    59                                                                               ##STR76##                  60                                                                               ##STR77##                                    61                                                                               ##STR78##                  62                                                                               ##STR79##                                    63                                                                               ##STR80##                  64                                                                               ##STR81##                                    65                                                                               ##STR82##                  66                                                                               ##STR83##                                    67                                                                               ##STR84##                  68                                                                               ##STR85##                                    69                                                                               ##STR86##                  70                                                                               ##STR87##                                    71                                                                               ##STR88##                  72                                                                               ##STR89##                                    73                                                                               ##STR90##                  74                                                                               ##STR91##                                    75                                                                               ##STR92##                  76                                                                               ##STR93##                                    77                                                                               ##STR94##                  78                                                                               ##STR95##                                    79                                                                               ##STR96##                  80                                                                               ##STR97##                                    81                                                                               ##STR98##                  82                                                                               ##STR99##                                    83                                                                               ##STR100##                 84                                                                               ##STR101##                                   85                                                                               ##STR102##                 86                                                                               ##STR103##                                   87                                                                               ##STR104##                 88                                                                               ##STR105##                                   89                                                                               ##STR106##                 90                                                                               ##STR107##                                   91                                                                               ##STR108##                 92                                                                               ##STR109##                                   93                                                                               ##STR110##                 94                                                                               ##STR111##                                   95                                                                               ##STR112##                 96                                                                               ##STR113##                                   97                                                                               ##STR114##                 98                                                                               ##STR115##                                   99                                                                               ##STR116##                 100                                                                              ##STR117##                                   101                                                                              ##STR118##                 102                                                                              ##STR119##                                   103                                                                              ##STR120##                 104                                                                              ##STR121##                                   105                                                                              ##STR122##                 106                                                                              ##STR123##                                   107                                                                              ##STR124##                 108                                                                              ##STR125##                                   109                                                                              ##STR126##                 110                                                                              ##STR127##                                   111                                                                              ##STR128##                 112                                                                              ##STR129##                                   113                                                                              ##STR130##                 114                                                                              ##STR131##                                   115                                                                              ##STR132##                 116                                                                              ##STR133##                                   117                                                                              ##STR134##                 118                                                                              ##STR135##                                   119                                                                              ##STR136##                 120                                                                              ##STR137##                                   121                                                                              ##STR138##                 122                                                                              ##STR139##                                   123                                                                              ##STR140##                 124                                                                              ##STR141##                                   125                                                                              ##STR142##                 126                                                                              ##STR143##                                   127                                                                              ##STR144##                 128                                                                              ##STR145##                                   129                                                                              ##STR146##                 130                                                                              ##STR147##                                   131                                                                              ##STR148##                 132                                                                              ##STR149##                                   133                                                                              ##STR150##                 134                                                                              ##STR151##                                   135                                                                              ##STR152##                 136                                                                              ##STR153##                                   137                                                                              ##STR154##                 138                                                                              ##STR155##                                   139                                                                              ##STR156##                 140                                                                              ##STR157##                                   141                                                                              ##STR158##                 142                                                                              ##STR159##                                   143                                                                              ##STR160##                 144                                                                              ##STR161##                                   145                                                                              ##STR162##                 146                                                                              ##STR163##                                   147                                                                              ##STR164##                 148                                                                              ##STR165##                                   149                                                                              ##STR166##                 150                                                                              ##STR167##                                   151                                                                              ##STR168##                 152                                                                              ##STR169##                                   153                                                                              ##STR170##                 154                                                                              ##STR171##                                   155                                                                              ##STR172##                 156                                                                              ##STR173##                                   157                                                                              ##STR174##                 158                                                                              ##STR175##                                   159                                                                              ##STR176##                 160                                                                              ##STR177##                                   161                                                                              ##STR178##                 162                                                                              ##STR179##                                   __________________________________________________________________________

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the infrared absorption spectrum (KBr tablet method) ofdisazo pigment No. 1 used in the present invention.

FIGS. 2 and 3 are enlarged sectional views illustrating the structuresof the electrophotographic elements of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As mentioned above, an electrophotographic element having a very highsensitivity can easily be prepared by using the disazo pigment of thepresent invention. Among them, disazo pigments Nos. 1, 16, 59, 60, 62,64, 71 and 75 are particularly preferable as a charge generatingmaterial.

The above disazo compounds are prepared by diazotizing4,4'-diaminotriphenyl amine as a starting material to form a tetrazoniumsalt thereof and effecting a coupling reaction with an appropriatecoupler. 4,4'-diaminotriphenyl amine is prepared, for example, by amethod disclosed in "Richarad Herz, Ber., 23, 2538".

The diazotization of 4,4'-diaminotriphenyl amine is carried out in adilute inorganic acid such as dilute hydrochloric acid or dilutesulfuric acid by adding sodium nitrite aqueous solution at -10° C. to10° C. This diazotization is completed in 30 minutes to 3 hours. To thereaction mixture, is added borofluoric acid, sodium borofluoride aqueoussolution or the like to precipitate as a tetrazonium salt. Theprecipitated crystal is preferably filtered out to be used in asucceeding reaction. The tetrazonium salt thus obtained is subjected toa coupling reaction with a coupler having the general formula (VIII). Inpractice, this reaction is carried out by dissolving a mixture of thetetrazonium salt and coupler in an organic solvent such asN,N-dimethylformaldehyde (DMF), dimethylsulfoxide or the like, andadding drop-wise an alkaline aqueous solution to the reaction solutionsuch as sodium acetate aqueous solution at about -10° C. to 40° C. Thisreaction is completed in about 5 minutes to 3 hours. After thecompletion of the reaction, the precipitated crystal is filtered out andis finally purified by an appropriate method (for example by washing,recrystalizing or the like with water and/or organic solvent).

The preparation of disazocompound of the present invention is furtherillustrated by the following Examples.

PREPARATION EXAMPLE 1 (PREPARATION OF DISAZO COMPOUND NO. 1)

4,4'-diaminotriphenylamine 5.51 g was added to hydrochloric acidcomprising water 10 ml and conc. hydrochloric acid 17 ml, and themixture was stirred for 1 hour at room temperature. The resultantmixture was then cooled to -2° C., and a solution obtained by addingsodium nitrite 3.31 g to water 12 ml was added drop-wise to the cooledmixture at a temperature of -2° C. to 1° C. for 30 minutes.

Thereafter, the resultant mixture was stirred at the same temperaturefor 1 hour and half, and undissolved portion (minute amount) was removedfrom the system. To this reaction liquor, was added 42% borofluoric acid20 ml, and the mixture was cooled to stand. The produced red-orangecolored needle-like crystal was filtered out, and was washed withethanol. The washed crystal was dried, thus producing tetrazoniumdifluoroborate 8.55 g(yield=90.3%). According to an infrared absorptionspectrum (KBr Tablet Method), an absorption band on the basis of N₂ ⁺was recognized at 2230 cm⁻¹.

0.95 g of the tetrazonium salt thus obtained and 1.26 g of2-hydroxy-3-naphthoic acid anilide as a coupler were dissolved in cooled230 ml of N,N-dimethylformamide. To this solution, was added drop-wise asolution comprising sodium acetate 0.66 g and water 10 ml at atemperature of 17°-21° C. for 5 minutes. Thereafter, the resultantmixture was stirred for 3 hours at room temperature. The producedprecipitate was filtered out, and was washed with N,N-dimethylformamide300 ml for 5 times and further with water 300 ml for 2 times. The washedprecipitate was dried at 80° C. under a reduced pressure of 2 mm Hg,thus obtaining 1.11 g (yield=67.4%) of the above disazo compound No. 1.

Various properties of the disazo compound No. 1 thus obtained were asfollows:

    ______________________________________                                        Melting Point: 300° C. or higher                                       Elementary Analysis:                                                                          C          H      N                                           ______________________________________                                        Measured Value  75.57      4.70   11.76                                       Calculated Value                                                                              75.80      4.53   11.90                                       ______________________________________                                    

The infrared absorption spectrum (KBr Tablet Method) of this compound isshown in FIG. 1.

PREPARATION EXAMPLES 2 TO 16

The same procedure as in the above Example 1 was repeated, except thatcompounds as mentioned in Table 1 were used as a coupler, and the disazocompounds thus obtained are shown in Table 1. Absorption of ν_(c=o)(amide I) of infrared absorption spectrum (KBr Tablet Method), meltingpoint and elementary analysis values with regard to the disazo compoundsobtained are also shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                                              Elementary Analysis (%)             Prepa-                                                                            Disazo                                C Measured                                                                           H Measured                                                                           N Measured            ration                                                                            Com-                                  Value  Value  Value                 Ex. pound                     ν.sub.c=o (cm.sup.-1)                                                             Melting                                                                            (Calculated                                                                          (Calculated                                                                          (Calculated           No. No. Coupler               (Amide I)                                                                            Point                                                                              Value) Value) Value)                __________________________________________________________________________     2  10                                                                                 ##STR180##           1670   more than 300° C.                                                           73.24  (73.37)                                                                       4.58  (4.68)                                                                         11.06  (11.09)         3   4                                                                                 ##STR181##           1670   more than 300° C.                                                           76.11  (76.12)                                                                       4.72  (4.85)                                                                         11.34  (11.51)         4  16                                                                                 ##STR182##           1670   more than 300° C.                                                           69.67  (69.95)                                                                       3.88  (3.95)                                                                         10.72  (10.98)         5  33                                                                                 ##STR183##           1680   290° C. (Decom- position                                                    68.66  (68.34)                                                                       3.82  (3.86)                                                                         13.89  (13.79)         6  62                                                                                 ##STR184##           1680   294° C. (Decom- position                                                    77.45  (77.18)                                                                       4.65  (4.86)                                                                         11.66  (11.91)         7  66                                                                                 ##STR185##           1670   more than 300° C.                                                           74.36  (74.63)                                                                       4.49  (4.46)                                                                         11.72  (11.87)         8  65                                                                                 ##STR186##           1675   more than 300° C.                                                           74.34  (74.63)                                                                       4.29  (4.46)                                                                         11.57  (11.87)         9  64                                                                                 ##STR187##           1670   more than 300° C.                                                           74.99  (74.63)                                                                       4.09  (4.46)                                                                         11.55  (11.87)        10  70                                                                                 ##STR188##           1680   more than 300° C.                                                           71.60  (71.77)                                                                       3.67  (3.86)                                                                         11.75  (11.77)        11  71                                                                                 ##STR189##           1680   more than 300° C.                                                           71.90  (71.77)                                                                       3.99  (3.86)                                                                         11.79  (11.77)        12  59                                                                                 ##STR190##           1680   more than 300° C.                                                           76.63  (76.95)                                                                       4.43  (4.60)                                                                         11.96  (12.24)        13  60                                                                                 ##STR191##           1680   more than 300° C.                                                           76.75  (76.95)                                                                       4.48  (4.60)                                                                         12.00  (12.24)        14  61                                                                                 ##STR192##           1670   more than 300° C.                                                           76.91  (76.95)                                                                       4.35  (4.60)                                                                         12.04  (12.24)        15  74                                                                                 ##STR193##           1680   more than 300° C.                                                           70.07  3.59  (3.78)                                                                         13.85  (14.11)        16  75                                                                                 ##STR194##           1680   more than 300° C.                                                           69.95  (70.39)                                                                       3.52  (3.78)                                                                         13.74  (14.11)        __________________________________________________________________________

The disazo pigment of the present invention is used as a chargegenerating material in a photosensitive layer of an electrophotographicelement. FIGS. 2 and 3 illustrate a typical structure of theelectrophotographic element.

The electrophotographic element of FIG. 2 comprises a laminated typephotosensitive layer 19 on an electroconductive substrate 11, saidphotosensitive layer 19 comprising a charge generating layer 15containing disazo pigment 13 as the main component and a charge transferlayer 17 containing charge transfer material as the main component.

In the electrophotographic element of FIG. 2, exposed light passesthrough a charge transfer layer to a charge generating layer 15 whereincharge is generated in disazo pigment 13. The charge thus generated istransferred by the charge transfer layer 17. Thus, the generation ofcharge necessary for light decay is effected in disazo pigment 13, andthe transfer of the generated charge is effected by the charge transferlayer 17.

The electrophotographic element shown in FIG. 3 is composed of aphotosensitive layer 19' on an electroconductive substrate 11, thephotosensitive layer 19' comprising essentially of disazo pigment 13,charge transfer material and insulative binder. The disazo pigment 13 isa charge generating material.

It is possible to modify the basic structure of the electrophotographicelement of FIG. 2, for example, by applying the charge generating layerand the charge transfer layer in reverse order.

The thickness of the charge generating layer 15 of the photosensitivelayer of FIG. 2 is preferably 0.01-5μ, more preferably 0.05-2μ. If thisthickness is less than 0.01μ, the generation of charge is notsatisfactory. On the other hand, if this thickness is more than 5μ, theresidual potential becomes too high for practical use.

The thickness of the charge transfer layer 17 is preferably 3-50μ, morepreferably 5-30μ. If this thickness is less than 3μ, a charged amount isinsufficient. On the other hand, if this thickness is more than 50μ, theresidual potential becomes too high for practical use.

The charge generating layer 15 contains disazo pigment expressed by theabove general formula as the main component, and further binder,plasticizer and the like. The amount of disazo pigment in the chargegenerating layer is more than 30% by weight, more preferably 50% byweight.

The charge transfer layer 17 contains charge transfer material andbinder as the main components and further plastilcizer and the like. Theamount of the charge transfer material in the charge transfer layer is10-95% by weight, preferably 30-90% by weight. If the amount of thecharge transfer material is less than 10% by weight, the transfer of thecharge is not substantially carried out. On the other hand, if thisamount is more than 95% by weight, the mechanical strength of thephotosensitive film is too poor for practical use.

The photosensitive layer 19' of the photosensitive element of FIG. 3 ispreferably 3-50μ, more preferably 5-30μ. The amount of the disazopigment in the photosensitive layer 19' is preferably less than 50% byweight, more preferably less than 20% by weight, and the amount of thecharge transfer material is preferably 10-95% by weight, more preferably30-90% by weight.

The essential feature of the present invention resides in the use ofspecific disazo pigments as expressed by the above general formula I,and other components such as electroconductive substrate, chargetransfer material and the like are the same as the conventionally knownmaterials. Examples of these materials are illustrated hereinafter.

Examples of the electroconductive substrate used in theelectrophotographic element of the present invention include: metallicplates such as aluminum, copper, zinc and the like; plastic sheets suchas polyester and the like; plastic film composite obtained by vapordepositing electroconductive materials such as aluminum, SnO₂ and thelike; or electroconductively treated paper and the like.

Examples of binders include: condensation type resins such as polyamide,polyurethane, polyester, epoxy resin, phenoxy resin, polyketone,polycarbonate and the like; vinyl polymers such as polyvinyl ketone,polystyrene, poly-N-vinyl carbazole, polyacrylamide, and the like. Anyresin can be used if it is insulative and adhesive.

Examples of plasticizers include halogenated paraffin,polybiphenylchloride, dimethylnaphthalene, dibutyl phthalate and thelike. Silicone oil may also be added to improve surface properties ofthe photosensitive material.

The charge transfer material includes a positive hole transfer materialand an electron transfer material. Examples of the hole transfermaterial include compounds as expressed by the following general formula(1) to (11). ##STR195## (wherein R₁ represents methyl, ethyl,2-hydroxyethyl or 2-chloroethyl; R₂ represents methyl, ethyl, benzyl orphenyl; and R₃ represents hydrogen, chlorine, bromine, alkyl having 1 to4 carbon atoms, alkoxy having 1 to 4 carbon atoms, dialkylamino ornitro.) ##STR196## (wherein Ar represents naphthalene ring, anthracenering, styryl and their substituents or pyridine ring furan ring, orthiophene ring; and R represents alkyl or benzyl.) ##STR197## (whereinR₁ represents alkyl, benzyl or phenyl; R₂ represents hydrogen, alkylhaving 1 to 3 carbon atoms, alkoxy having 1 to 3 carbon atoms,dialkylamino, diaralkylamino or diarylamino; n represents an integer of1 to 4; when n is 2 or more, R₂ may be the same or different; and R₃represents hydrogen or methoxy.) ##STR198## (wherein R₁ represents alkylhaving 1 to 11 carbon atoms, substituted or non-substituted phenyl orheterocyclic group; R₂ and R₃ may be the same or different and representhydrogen, alkyl having 1 to 4 carbon atoms, hydroxyalkyl, chloroalkyl,substituted or non-substituted aralkyl; R₂ and R₃ may be bonded witheach other to form a heterocyclic ring containing nitrogen; R₄ may bethe same or different and represent hydrogen, alkyl having 1 to 4 carbonatoms, alkoxy or halogen.) ##STR199## (wherein R represents hydrogen ora halogen atom; and Ar represents substituted or non-substituted phenyl,naphthyl, anthryl or carbazolyl.) ##STR200## (wherein R₁ representshydrogen, halogen, cyano, alkoxy having 1 to 4 carbon atoms or alkylhaving 1 to 4 carbon atoms; Ar represents ##STR201## wherein R₂represents alkyl having 1 to 4 carbon atoms, R₃ represents hydrogen,halogen, alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbonatoms or dialkyl amino, n is an integer of 1 or 2; when n is 2, R₃ maybe the same or different; R₄ and R₅ represent hydrogen, substituted ornon-substituted alkyl having 1 to 4 carbon atoms or substituted ornon-substituted benzyl group.) ##STR202## (wherein R representscarbazolyl, pyridyl, thienyl, indolyl, furyl, or substituted ornon-substituted phenyl, styryl, naphthyl or anthryl group; thesesubstituents are selected from the group of dialkylamino, alkyl, alkoxy,carboxyl or its ester, halogen atom, cyano, aralkylamino,N-alkyl-N-aralkylamino, amino, nitro and acetyl amino groups.)##STR203## (wherein R₁ represents a lower alkyl or benzyl group; R₂represents hydrogen, lower alkyl, lower alkoxy, halogen, nitro, amino,or amino group substituted with lower alkyl or benzyl; and n is aninteger of 1 or 2.) ##STR204## (wherein R₁ represents hydrogen, alkyl,alkoxy or halogen; R₂ and R₃ represent alkyl, substituted ornon-substituted aralkyl, or substituted or non-substituted aryl group;R₄ represents hydrogen or substituted or non-substituted phenyl; and Arrepresents phenyl or naphthyl group.) ##STR205## (wherein n is aninteger of 0 or 1; R₁ represents hydrogen, alkyl or substituted ornon-substituted phenyl; A represents ##STR206## 9-anthryl, orsubstituted or non-substituted N-alkylcarbazolyl group, wherein R₂represents hydrogen, alkyl, alkoxy, halogen or ##STR207## wherein R₃ andR₄ represent alkyl, substituted or non-substituted aralkyl, orsubstituted or non-substituted aryl group, and R₃ and R₄ may form aring; and m is an integer of 0, 1, 2 or 3, when m is 2, R₂ may be thesame or different.) ##STR208## (wherein R₁, R₂ and R₃ are hydrogen,lower alkyl, lower alkoxy, dialkylamino, or halogen; and n is 0 or 1.)

Examples of the compound expressed by the general formula (1) include:

9-ethylcarbazole-3-aldehyde-1-methyl-1-phenylhydrazone,

9-ethylcarbazole-3-aldehyde-1-benzyl-1-phenylhydrazone,

9-ethylcarbazole-3-aldehyde 1,1-diphenylhydrazone, and the like.

Examples of the compound expressed by the general formula (2) include:

4-diethylaminostyrene-β-aldehyde-1-methyl-1-phenylhydrazone,

4-methoxynaphthalene-1-aldehyde-1-benzyl-1-phenylhydrazone, and thelike.

Examples of the compound expressed by the general formula (3) include:4-methoxybenzaldehyde 1-methyl-1-phenylhydrazone,2,4-dimethoxybenzaldehyde 1-benzyl-1-phenylhydrazone,

4-diethylaminobenzaldehyde 1,1-diphenylhydrazone,

4-methoxybenzaldehyde 1-benzyl-1-(4-methoxy)phenyl hydrazone,4-diphenylaminobenzaldehyde-1-benzyl-1-phenylhydrazone,

4-dibenzylaminobenzaldehyde 1,1-diphenylhydrazone and the like.

Examples of the compound expressed by the general formula (4) include:

1,1-bis(4-dibenzylaminophenyl)propane,

tris(4-diethylaminophenyl)methane,

1,1-bis(4-dibenzylaminophenyl)propane,

2,2'-dimethyl-4,4'-bis(diethylamino)-triphenylmethane and the like.

Examples of the compound expressed by the general formula (5) include:

9-(4-diethylaminostyryl)anthracene,

9-bromo-10-(4-diethylaminostyryl)anthracene, and the like.

Examples of the compound expressed by the general formula (6) include:

9-(4-dimethylaminobenzylidene)fluorene,

3-(9-fluorenylidene)-9-ethylcarbazole, and the like.

Examples of the compound expressed by the general formula (7) include:

1,2-bis(4-diethylaminostyryl)benzene,

1,2-bis(2,4-dimethoxystyryl)benzene and the like.

Examples of the compound expressed by the general formula (8) include:

3-styryl-9-ethylcarbazole,

3-(4-methoxystyryl)-9-ethylcarbazole, and the like.

Examples of the compound expressed by the general formula (9) include:4-diphenylaminostilbene,

4-dibenzylaminostilbene, 4-ditolylaminostilbene,

1-(4-diphenylaminostyryl)naphthalene,

1-(4-diethylaminostyryl)naphthalene, and the like.

Examples of the compound expressed by the general formula (10) include:

4'-diphenylamino-alpha-phenylstilbene,

4'-methylphenylamino-alpha-phenylstilbene, and the like.

Examples of the compound expressed by the general formula (11) include:

1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline,

1-phenyl-3-(4-dimethylaminostyryl)-5-(4-dimethylaminophenyl)pyrazoline,and the like.

Other examples of positive hole transfer material include: oxadiazolecompounds such as

2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole,

2,5-bis(4-(4-diethylaminostyryl)phenyl)-1,3,4-oxadiazole,

2-(9-ethylcarbazolyl-3-)-5-(4-diethylaminophenyl)-1,3,4-oxadiazole, andthe like;

low molecular oxazole compounds such as2-vinyl-4-(2-chlorophenyl)-5-(4-diethylaminophenyl)-oxazole,2-(4-diethylaminophenyl)-4-phenyloxazole, and the like; and

high molecular compounds such as poly-N-vinyl carbazole, halogenatedpoly-N-vinyl carbazole, polyvinyl pyrene, polyvinyl anthracene, pyreneformaldehyde resin, ethylcarbazole formaldehyde resin, and the like.

Examples of electron transfer material include: chloroanil, bromoanil,tetracyanoethylene, tetracyanoquinonedimethane,

2,4,7-trinitro-9-fluorenone,

2,4,5,7-tetranitro-9-fluorenone,

2,4,5,7-tetranitro-xanthone,

2,4,8-trinitrothioxanthone,

2,6,8-trinitro-4H-indeno(1,2-b)thiophene-4-on,

1,3,7-trinitrodibenzothiophene-5,5-dioxide, and the like.

These charge transfer materials are used alone or in the form of amixture of two or more.

With regard to the electrophotographic elements as prepared above, asadhesive layer or barrier layer may optionally be applied between anelectroconductive substrate and a photosensitive layer. Examples ofthese layers include polyamide, nitrocellulose, aluminum oxide and thelike. The thickness of the layer is preferably not more than 1μ.

The electrophotographic element as shown in FIG. 2 is prepared byvapor-depositing disazo pigment on an electroconductive substrate inaccordance with vacuum vapor depositing method as disclosed in U.S. Pat.Nos. 3,973,959 and 3,996,049 or coating and drying on anelectroconductive substrate a dispersion of disazo pigment particles inan appropriate solvent optionally having a binder dissolved; and thencoating and drying a solution containing charge transfer material andbinder on the charge generating layer, the surface of which mayoptionally be subjected to a buff polishing as disclosed in JapanesePatent Laid Opent No. 51-90827, or the thickness of which may beregulated.

The electrophotographic element as shown in FIG. 3 is prepared bydispersing disazo pigment particles in a solution having charge transfermaterial and binder dissolved, coating the dispersion on anelectroconductive substrate and drying. In any case, disazo pigment usedin the present invention is powdered by a ball mill or the like to aparticle size of not more than 5μ, preferably not more than 2 u. Coatingcan be effected by ordinary method by means of doctor blade, dipping,wire bar and the like.

Copying by the electrophotographic element of the present invention canbe effected by developing after charging and explosing thephotosensitive layer surface and, if necessary, transferring thedeveloped image to paper and the like.

As clearly seen from the above description and the following Examples,the electrophotographic element of the present invention using disazopigment having the triphenylamine structure as a charge generatingmaterial can be easily produced and has a high sensitivity in comparisonwith the conventional electrophotographic elements. In addition to theseadvantages, performances of the electrophotographic element of thepresent invention are stable even if it is repeatedly used a greatnumber of times.

The present invention is further illustrated by the following Examples,but the present invention should not be limited thereto.

EXAMPLE 1

76 parts by weight of disazo pigment NO. 75, 1260 parts by weight oftetrahydrofuran solution (solid content=2%) of polyester resin ("Byron200" manufactured by Toyo Boseki Ltd.), and 3700 parts by weight oftetrahydrofuran are powdered and mixed in a ball mill. The dispersionthus obtained was coated on an aluminum surface of an aluminum-depositedpolyester base (electroconductive substrate) by a doctor blade, and thecoated film was allowed to stand for drying, thereby forming a chargegenerating layer having a thickness of about 1 μm.

On this charge generating layer, was coated a solution prepared bydissolving and mixing 2 parts by weight of 9-ethylcarbazole-3-aldehyde1-methyl-1-phenylhydrazone, 2 parts by weight of polycarbonate resin("Panlight K-1300" manufactured by Teijin Co. Ltd.) and 16 parts byweight of tetrahydrofuran by a doctor blade, and the coated film wasdried at 80° C. for 2 minutes and 105° C. for 5 minutes, thereby forminga charge transfer layer having a thickness of about 18 μm. The laminatedtype electrophotographic element No. 1 thus prepared is shown in FIG. 2.

EXAMPLES 2 TO 5

Electrophotographic elements Nos. 2 to 5 were prepared in the samemanner as in Example 1, except that disazo pigments as shown in thefollowing Table 2 were used in place of disazo pigment No. 75 used inExample 1.

EXAMPLES 6 TO 10

Electrophotographic elements Nos. 6 to 10 were prepared in the samemanner as in Example 1, except that1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline wasused as a charge transfer material and disazo pigments as shown in thefollowing Table 2 were used.

EXAMPLES 11 TO 15

Electrophotographic elements Nos. 11 to 15 were prepared in the samemanner as in Example 1, except that 9-(4-diethylaminostyryl)anthracenewas used as a charge transfer material and disazo pigments as shown inthe following Table 2 were used.

EXAMPLES 16 TO 20

Electrophotographic elements Nos. 16 to 20 were prepared in the samemanner as in Example 1, except that4'-diphenylamino-alpha-phenylstilbene was used as a charge transfermaterial and disazo pigments as shown in the following Table 2 wereused.

The thus prepared electrophotographic elements Nos. 1 to 20 weresubjected to -6 KV corona discharge for 20 seconds by an electrostaticcopying paper tester (SP428 Type produced by Kawaguchi Denki Works), andwere charged negatively. Thereafter, these elements were left to standin the dark for 20 seconds to measure the surface potential Vpo (V) atthat time, and were exposed to radiation of a tungsten lamp so that theintensity of surface illumination may become 4.5 Lux. Then, the time(sec.) required until the surface potential was reduced to 1/2 of Vpowas measured, and the exposure amount E_(1/2) (Lux-sec) was calculated.The results thus obtained are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                 Photo-   Disazo            E 1/2                                     Example  sensitizer                                                                             Pigment    Vpo(V) (Lux.sec)                                 ______________________________________                                        1        1        75         -784   1.7                                       2        2        60         -1367  2.9                                       3        3        16         -1201  4.5                                       4        4        83         -838   5.7                                       5        5        100        -1095  8.3                                       6        6        1          -1062  4.3                                       7        7        62         -760   2.2                                       8        8        94         -882   1.9                                       9        9        59         -784   0.7                                       10       10       114        -186   9.2                                       11       11       33         -1394  6.5                                       12       12       97         -1186  9.3                                       13       13       116        -1114  14.3                                      14       14       60         -1530  3.1                                       15       15       75         -1066  2.7                                       16       16       71         -1266  1.0                                       17       17       64         -1174  1.5                                       18       18       19         -838   2.6                                       19       19       50         -946   4.2                                       20       20       106        -1204  3.2                                       ______________________________________                                    

The electrophotographic elements Nos. 4 and 7 were set in anelectrophotographic copying machine (Ricopy-P-500 Type produced by RICOHK.K.), and the image-formation was repeated 10,000 times. As theresults, each electrophotographic element was found to form a clear-outimage. It should be understood from this results that theelectrophotographic element of the present invention is excellent indurability.

What is claimed is:
 1. A photosensitive material for use inelectrophotography, comprising: an electroconductive substrate; aphotosensitive layer on said substrate, said photosensitive layercontaining a disazo compound having the formula (V), ##STR209## whereinA is selected from the group consisting of radicals of the formulas(VI), (VII), (VIII), (IX), (X), (XI) and (XII), ##STR210## wherein X₁ is--OH, ##STR211## or --NHSO₂ --R₃ in which R₁ and R₂ are hydrogen, alkylor substituted alkyl, and R₃ is alkyl, substituted alkyl, aryl orsubstituted aryl; Y₁ is hydrogen, halogen, alkyl, substituted alkyl,alkoxy, substituted alkoxy, carboxyl, sulfo, sulfamoyl, substitutedsulfamoyl, ##STR212## in which R₄ is hydrogen, alkyl, substituted alkyl,phenyl or substituted phenyl, Y₂ is cyclic hydrocarbon, substitutedcyclic hydrocarbon, heterocycle or substituted heterocycle, R₅ is cyclichydrocarbon, substituted cyclic hydrocarbon, heterocycle, substitutedheterocycle, styryl, or substituted styryl, and R₆ is hydrogen, alkyl,substituted alkyl, phenyl, substituted phenyl, or ##STR213## forms aring, Z is a cyclic hydrocarbon, substituted cyclic hydrocarbon,heterocycle or substituted heterocycle;n is an integer of 1 or 2; m isan integer of 1 or 2; ##STR214## in which R₇ is hydrocarbon orsubstituted hydrocarbon group, and X₁ is the same as defined above;##STR215## in which R₈ is alkyl, carbamoyl, carboxyl or ester thereof,and Ar₁ is a cyclic hydrocarbon or substituted cyclic hydrocarbon, andX₁ is the same as defined above.
 2. The electrophotographic elementaccording to claim 1, wherein said coupler residue A has the formula(VII), (X), (XI) or (XII), and X₁ is hydroxyl.
 3. Theelectrophotographic element according to claim 1, wherein said couplerresidue A has the formula (XV), ##STR216## wherein Y₁ and Z are the sameas defined above.
 4. The electrophotographic element according to claim1, wherein said coupler residue A has the formula (XVI), ##STR217##wherein Z, Y₂ and R₂ are the same as defined above.
 5. Theelectrophotographic element according to claim 1, wherein said couplerresidue A has the formula (XVII) or (XVIII), ##STR218## wherein Z, R₂,R₅ and R₆ are the same as defined above, and R₁₀ is the same as thesubstituent for Y₂.
 6. The electrophotographic element according toclaim 1, in which A is ##STR219##
 7. The electrophotographic elementaccording to claim 1, in which A is ##STR220##
 8. Theelectrophotographic element according to claim 1, in which A is##STR221##
 9. The electrophotographic element according to claim 1, inwhich A is ##STR222##
 10. The electrophotographic element according toclaim 1, in which A is ##STR223##
 11. The electrophotographic elementaccording to claim 1, in which A is ##STR224##
 12. Theelectrophotographic element according to claim 1, in which A is##STR225##
 13. The electrophotographic element according to claim 1, inwhich A is ##STR226##
 14. The electrophotographic element according toclaim 1, in which Z is benzene, naphthalene, indole, carbazole,benzofuran and dibenzofuran and the substituent thereon is halogen; Y₂and R₅ are phenyl, naphthyl, anthryl, pyridyl, thienyl, furyl, indolyl,benzofuranyl, carbazolyl, dibenzofuranyl, and the substituent thereon isalkyl, alkoxy, halogen, dialkylamino, diaralkylamino, halomethyl, nitro,cyano, carboxyl or ester thereof, hydroxyl and sulphonate; thesubstituent for R₄ is halogen; R₇ and R⁹ are alkyl, benzyl, phenyleither unsubstituted or substituted with alkyl, alkoxy, halogen,hydroxyl or nitro; and Ar₁ is phenyl or naphthyl either unsubstituted orsubstituted with alkyl, alkoxy, nitro, halogen, cyano or dialkylamino.15. The electrophotographic element according to claim 1, in which saidphotosensitive layer comprises a charge generating layer containing saiddisazo compound, and a charge transfer layer containing a chargetransfer material, said charge generating layer having a thickness offrom 0.01 to 5μ and containing more than 30% by weight of said disazocompound, said charge transfer layer having a thickness of from 3 to 50μand containing from 10 to 95% by weight of said charge transfermaterial.
 16. The electrophotographic element according to claim 1, inwhich said photosensitive layer is a monolayer having a thickness offrom 3 to 50μ and consisting essentially of said disazo compound, chargetransfer material and insulative binder, said photosensitive layercontaining less than 50% by weight of said disazo compound and from 10to 95% by weight of said charge transfer material.